1. Field of the Invention
The present invention relates a process for removing chemical oxygen demand (COD) from wastewater by chemical oxidation using Fenton's reagent. More particularly, it relates to a chemical oxidation process utilizing a fluidized bed to reduce the sludge production and to improve the COD removal efficiency.
2. Description of the Related Arts
To meet strict laws on environmental protection, the COD in effluent discharged from factories must be reduced to a significant extent. A feasible method, known as Fenton's method, has been widely used for the reduction of COD in wastewater. According to Fenton's method, hydrogen peroxide and iron(II) compounds are added to wastewater so that the organic pollutants contained in wastewater are oxidized by the hydroxyl free radicals (OH.sup..multidot.) produced by the reaction between the hydrogen peroxide and the ferrous ion. However, in practical applications, Fenton's method is not completely satisfactory and the disadvantages thereof are summarized as below:
1. The necessity of addition of chemical reagents such as hydrogen peroxide, ferrous ions, acids and alkalis makes the practice of this method costly.
2. A significant amount of iron(III) hydroxide sludge is produced. This necessitates a further treatment of the iron hydroxide sludge. Such treatment is also costly.
The cost of ferrous ions and sludge treatment is about 1/4-1/2 of total operational cost. Conventionally, the produced iron hydroxide sludge is separated from wastewater by using sedimentation or flotation techniques. However, this has burdened the treatment facilities with a large quantity of sludge and leads to the problem of disposing the sludge.